# NTSB NYC03LA033: MBB BK 117 A-4, N951AM, Albany, NY, December 26, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: December 26, 2002, 14:40 local (19:40 UTC) - Place: Albany, NY - Coordinates: 42.651668, -73.77861 - Nearby events: https://openairdocs.org/map.md?lat=42.6517&lon=-73.7786&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report June 30, 2004 - Report: Approved by Office Director - Parties: FAA - NTSB case key (mKey): 56249 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC03LA033 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/56249/pdf - Page: https://openairdocs.org/ntsb/NYC03LA033 ## Probable cause The inadvertent encounter with a downdraft during engine start, which flexed the main rotor blades and subsequently damaged the tail boom assembly. A factor related to the accident was the failure of the operator to comply with a service bulletin. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - On ground/water encounter with weather, standing - starting engine(s) - weather condition - downdraft (cause) - maintenance,service bulletin/letter - not complied with, company maintenance personnel (contributing factor) - misc rotorcraft,main rotor/tail boom contact ## Analysis The helicopter was positioned on the hospital rooftop helipad facing in a southerly direction. After the medical crew boarded the helicopter, the number 1 engine was started. As the main rotor blades began to turn, an unexpected gust of wind traveling over the rooftop caused the blades to flap excessively. The pilot then heard a series of thumps, and aborted the start. Inspection of the helicopter revealed that one of the main rotor blades had come in contact with the left vertical stabilizer, damaging the tail boom, main rotor blades, and the left vertical stabilizer. On November 30, 1990, the helicopter manufacturer issued service bulletin SB-MBB-BK-30-103, which called for a triangle section to be cut out of the stabilizer fin assembly, in an area where a potential strike from a main rotor blade could occur, and replaced with a foam core insert. The operator did not apply the service bulletin to the accident helicopter. The winds reported by the pilot at the time of the engine start were from 340 degrees at 14 knots, gusting to 24 knots. ## Factual narrative On December 26, 2002, at 1440 eastern standard time, an MBB (Eurocopter) BK 117 A-4 helicopter, N951AM, operated by Rocky Mountain Holdings LLC, was substantially damaged during engine start-up on a roof-top helipad at the Albany Medical Center, Albany, New York. The certificated commercial pilot and two medical flight personnel were not injured. Visual meteorological conditions prevailed, and a company visual flight rules flight plan was filed for the medevac flight conducted under 14 CFR Part 91. According to the pilot, the helicopter was positioned on the helipad facing in a southerly direction. After the medical crew boarded the helicopter, the number 1 engine was started. As the main rotor blades began to turn, an unexpected gust of wind traveling over the rooftop of the hospital helipad caused the blades to flap excessively. The pilot then heard a series of thumps, and the start was aborted. Inspection of the helicopter by a Federal Aviation Administration inspector revealed that one of the main rotor blades had come in contact with the left vertical stabilizer, damaging the tail boom, main rotor blades, and the left vertical stabilizer. On November 30, 1990, the helicopter manufacturer issued service bulletin SB-MBB-BK-30-103, which called for a triangle section to be cut out of the stabilizer fin assembly, in an area where a potential strike from a main rotor blade could occur, and replaced with a foam core insert. The service bulletin included the following information, "During start-up and shutdown of the engines, the main rotor blades can strike into the endplates if heavy downdrafts occur while the rotor is accelerating from or slowing down to standstill. The presence of very heavy downdrafts which can cause damage to the main rotor blades and to the endplates upon engine startup and shutdown, must be reckoned with at some operational locations, especially between high buildings. Downward deflections of the main rotor blades which can cause the endplates to be struck cannot be rule out during heavy downdrafts. For this reason, the endplate shall be modified in the potential strike area so that a piece of the endplate will be struck out upon impact, without the main rotor sustaining damage." The service bulletin had not been applied to the accident helicopter. The winds reported by the pilot at the time of the engine start were from 340 degrees at 14 knots, gusting to 24 knots. The winds reported by an airport 5 miles north of the heliport, at 1451, were from 300 degrees at 19 knots, gusting to 26 knots. ## Aircraft - Registration: N951AM (not matched to a registry record) - Reported make and model: MBB BK 117 A-4 - Category: Helicopter - Serial number: 7071 - Airframe hours: 6498 - Engines: Garrett-AiResearch LTS101-650B1 650 horsepower turbo shaft; Garrett-AiResearch LTS101-650B1 650 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Registered owner: Rocky Mountain Holdings - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, December 20, 2002, 7 hours before - Departed: NK64, Albany, NY - Flight plan: Company VFR - Airport: NONE ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; injuries: none; commercial; medical: class 2, valid medical--w/ waivers/lim; seat: rear; flight hours: 5,000 total, 450 in this make and model, 3,500 as pilot in command ## Weather - Conditions: Visual (VMC), Night - Wind: 300° at 19 knots, gusting 26 - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 30 °F, dew point 21 °F - Altimeter: 29.87 inHg - Observed at: ALB, 5 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20021226037469A](https://openairdocs.org/incident/20021226037469A), Dec 26, 2002: Bolkms BK117A4, Albany, NY, Substantial damage. (-23) During engine start the rotor blades were flexing from the wind. As the rotor started to turn, one blade struck the left vertical stabilizer, causing the… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.